As a conventional example of a head support mechanism using a floating type head, a magnetic disk apparatus such as a hard disk apparatus is explained by referring to FIG. 12.
FIG. 12 is a plan view showing a configuration of a head support mechanism of a conventional magnetic disk apparatus, and the relation of the head support mechanism and a disk. A head support mechanism 108 is composed of a suspension 102 of relatively low rigidity, a flat spring 103, an arm 104 of relatively high rigidity, a slider 101 provided at one end portion of the suspension 102 and at a side facing a disk 107, and a head (not shown) mounted on this slider 101. The suspension 102 is designed at a relatively low rigidity, and the other end portion is folded to compose the flat spring 103, and this flat spring 103 is connected to the arm 104. The arm 104 is rotatably supported by a bearing part 105, and the head support mechanism 108 can be rotated in a specified angle range in a direction parallel to the disk 107 surface by driving means 106 attached to the arm 104. The head support mechanism 108, bearing part 105, and driving means 106 are combined to compose a head drive device 150.
The disk 107 is rotated at a specified speed by rotation driving means 109. At the time of recording or reproducing, owing to the balance of buoyancy by an air stream caused by rotation of the disk 107 and thrusting force of thrusting the slider 101 to the disk 107 surface side, the slider 101 floats at a specific flying height, and the head records or reproduces at this specific flying height. The thrusting force of the slider 101 to the disk 107 surface side is mainly applied from the flat spring 103 of the head support mechanism 108.
That is, at the time of recording or reproduction, the head support mechanism 108 is rotated about the bearing part 105 by the driving means 106. When the head mounted on the slider 101 flys at a specific flying height from the surface of the disk 107, it is positioned in a specified track, and recording or reproducing is carried out.
The magnetic disk apparatus shown in FIG. 12 is a magnetic disk apparatus generally known as a contact start-stop system (CSS system). While rotation of the disk 107 is stopped, the slider 101 contacts with the surface of the disk 107, and when recording or reproducing, the slider 101 floats from the surface of the disk 107. In this CSS system, the recordable region of the disk 107 is an annular region A shown in FIG. 12, and a central annular region B is a waiting region for the slider 101 while rotation of the disk 107 is stopped. When rotation of the disk 107 stops, the slider 101 is moved to region B while floating, and as rotation of the disk 107 slows down, the air stream between the disk 107 and the slider 101 decreases and the buoyancy declines, and finally the slider 101 contacts with the surface of the disk 107 and stops.
Accordingly, in the CSS system, as compared with the surface of region A of the disk 107, the surface of region B is rough, and the slider 101 is prevented from being sucked to the surface of the disk 107 when stopping rotation of the disk 107. If suction occurs, the disk 107 is damaged mechanically and magnetically at the time of start, and it is intended to prevent this inconvenience.
As a method of preventing suction, for example, a load-unload system (L/UL system) is known, in which the slider is moved away from the disk surface when stopping rotation of the disk, and kept in another place. FIG. 13 is a schematic perspective view of this L/UL system magnetic disk apparatus. The elements as in FIG. 12 are identified with the same reference numerals. When stopping rotation of a disk 112, a head support mechanism 108 rotates about the center of a bearing part 105, and a suspension 102 rides on a taper portion 110a of a head holding part 110 provided at the outside of the disk 112. As a result, if the entire surface of the disk 112 is smooth, the slider 101 is not sucked to the disk.
In these head support mechanisms, a specified load is applied to the slider by the flat spring mainly by the thrusting force to thrust in the disk direction, and the suspension has a flexibility. Accordingly, if vertical motion of the disk occurs at the time of recording or reproducing in the disk, the slider can be stably lifted and the head is prevented from being deviated from the specified track to be in an off-track state, and it is also intended to follow up the vertical motion of the disk sufficiently. It is therefore required that the thrusting force necessary for thrusting the slider in the disk surface direction should be securely provided from the flat spring. Besides, since the buoyancy of the slider varies with the manufacturing fluctuations, it is also required to prevent variation of the thrusting force of the slider to the disk surface direction. For this purpose, the suspension may be provided with a notch or formed in a thin plate structure to lower the rigidity and decrease the spring constant, and the head support mechanism is provided with a certain flexibility to absorb fluctuations of the thrusting force.
However, when the suspension is formed in a thin plate structure, the frequency of main resonance point, or the so-called resonance frequency is lowered. As a result, when the head support mechanism is rotated to position at a specified track, a vibration mode such as torsion occurs. It takes a certain time until settling at this vibration mode occurs, and hence the access time cannot be shortened.
Further, in the conventional head support mechanism, its center of gravity is positioned near the head location rather than the flat spring. Accordingly, if a strong impact is applied to the magnetic disk apparatus from outside, the balance of buoyancy by an air stream caused by rotation of the disk and thrusting force of thrusting the slider to the disk side is broken in the slider area, and the slider is likely to pop out from the disk surface. When such popping phenomenon occurs, the slider may collide against the disk, and the disk may be broken magnetically or mechanically. On the other hand, there is an increasing demand for a smaller and thinner magnetic disk apparatus. Hence there is demand for the head support mechanism to be made thinner in order to realize a thin apparatus. Such problems are not limited to the magnetic disk apparatus, but are commonly seen in the disk apparatus having a floating head, for example, an optical disk apparatus or a magneto-optical disk apparatus.